In an instant messaging system, a user needs to obtain online information of the user's buddies upon logging in the instant messaging system. Meanwhile, login information of the user is sent to those users who have added the user as their buddy. If the online status of the user changes, information regarding change of the online status of the user also needs to be sent to those users who have added the user as their buddy.
With regards to management of user online information, a centralized management approach under current techniques typically employs a designated user information management server to manage the user online information. When a user logs in a system, the user's login information is sent to and managed by the user information management server. Whether it is during user login, change of online status after a user's login, or exchange of instant messages between users, any searching for the online information of the user's contacts needs to go through the user information management server. Therefore, not only the workload of the user information management server is increased, but the network overhead is also greatly increased.
With an ever-increasing number of online users in large-scale instant messaging systems, a single user information management server is no longer able to meet the demand of centralized management of all the user online information. Online information of the users is distributed amongst multiple user information management servers. A search for user online information thus needs to be carried out on multiple user information management servers, resulting in decreased search efficiency. As the number of users further increases, the search efficiency of user information management servers will further decrease substantially. This leads to the deterioration of the management of user online information, which becomes the bottleneck of the entire instant messaging system.